Method and apparatus for operating steam generators



Dec. 8, 1942. Q CAMPBELL 2,304,538

METHOD AND APPARATUS FOR OPERATING STEAM GENERATORS Filed Feb. 1. 1941 l/ I// I II II/\I/ I //l III/l II\ III III/II II I/ I] l/ [I I I III I LIIII/II III INVENTOR.

Patented Dec. 8, 1942 METHOD AND APPARATUS FOR OPERATING STEAM GENERATORS Osmon B. Campbell, St. Joseph, Mo. Application February 1, 1941, Serial No. 377,044

1 Claim.

This invention relates to steam generating apparatus of the forced circulation or series type and is a modification of the once through system in that part of the working fluid, comprising a mixture of water and steam, is continually withdrawn from the sy tem, a high vel ci y, and then returned thereto, at a point farther back,. and caused to retraverse a part of its course, establishing circulation in that part of the system in which most of the evaporation takes place.

One object of the invention is to establish a more stable condition of the working fluid and to provide a fluid of suitable condition to be handled by the superheating section, to the end of attaining better control of the final temperature of the steam.

Another object of the invention is to provide a generating section having definite limits and occupying a definite portion of the system, regardless of the load, or other operating conditions, to effect improved operation of this class of apparatus.

Another object is to provide a certain reserve power, a factor, which is typically absent in this general class of apparatus, and this is accomplished by the manner in which the fluid is treated in the evaporating section. Water forms but a part of the fluid in this section, and, there is, therefore, a considerable amount of steam in storage; and further, the water, all at steaming temperature, is swept rapidly over a large area of heating surface, so that rapid steaming is provided, up to the maximum capacity of the section. The water rate is not dependent upon the amount of water in the section, but upon its rapid movement over the surface, and there is no possibility of the section becoming waterlogged, when there is a sudden large increase in load. The water content of the fluid in this section is determined by the condition within the superheating section and the final temperature of the steam, and is such, that evaporation can be completed and the fluid heated to the desired temperature in the superheating section. When the final temperature of the steam rises to a certain point, more water is supplied to the system, and after traversing the preheating section, enters the evaporating section to build up the water content of the fluid therein, and pass a fluid of greater water content on to the superheating section. The effect is that water is then carried farther along in the superheating section, the temperature of the steam reduced, and the water supply to the system stopped.

I use the terms preheating, evaporating, and superheating sections only in a nominal sense and as signifying the principal function of the respective portions of the system. In some cases there may be considerable evaporation in the preheating section; evaporation is not completely accomplished in the evaporating section; and evaporation is a function of the fore part of the superheating section, and the distance water is carried by the steam into this section is determined by the final temperature of the steam.

Regulating the feed water to control the temperature of the steam is an old method, but as previously used is not fully effective. It has been the experience that during operation at partial load, too much water will frequentlyadvance too far along the tube and then the temperature will suddenly fall below the desired point and the pressure will also fall. This occurs because the column of mixed water and steam, which follows the steam in the tube, is too short and too. dense to effect a gradual reduction in the temperature. By recirculating part of the steam, I correct this condition by providing a long column of the mixture of gradually increasing density to bring about a gradual reduction in temperature.

The circulation is continuous while the apparatus is functioning to produce steam and may continue or be interrupted with little diflerence in effect during periods, when neither water nor heat are being supplied, and the output of steam is due only to accumulated heat and pressure.

A generator embodying this invention is shown in diagrammatic form in the accompanying drawing, in which I design-ates a housing, in which is the boiler tube 2; 3 designates a tube through which heat is supplied to the boiler tube; 4 an exhaust gas passage; 5 a pipe through which water is supplied to the motor-pump unit 6, which forces water to the boiler. Numeral l designates a thermal-electric device, which is responsive to the final temperature of the steam in the delivery pipe 8, and is adapted to control the pump unit 6, by controlling the circuit, which includes said device 1, the conductors 9, l0, and lo, the grounded battery H, and said pump unit 6. Numeral I2 designates a motor pump unit, which continually draws fluid, comprising a mixture of water and steam, from the boiler tube through the pipe I3, and returns said fluid through the pipe l4, establishing circulation in that part of the system between the points I5 and Hi. This motor-pump unit receives current from the battery ll, through the conductors l0 and l1; l8 designates a thermal switch, which is adapted to close a circuit, including the battery II, the conductors 9, HI, ID and I9, and the motor-pump unit 6, to supply water to the system, regardless of the final temperature of the steam, and functions only to meet minimum water requirements. 20 designates a manually operated switch to the battery.

I have-shown a single pump for creating circulation in the evaporating section, but when the boiler tube is very long and the resistance high, more than one pump might be used with successive zones of circulation, or tubes in parallel relation might be used to reduce resistance.

I claim:

The method of operating a vapor generator of the forced flow type, which consists in continuously withdrawing a mixture of liquid and Vapor from the boiler tube and returning said mixture of liquid and vapor to the boiler tube at a point farther back, without separation of liquid and vapor.

OSMON B. CAMPBELL. 

